End cap for segmented stator

ABSTRACT

A stator for an electromagnetic machine includes a plurality of discrete and individually wound stator segments having end caps positioned on the segments. The end caps have legs for positioning the end cap on the segments with an interference fit. The end caps have angled surfaces to facilitate winding of wire on the segments. The end caps have male and female couplings that mate together to couple adjacent segments together. The end caps have fingers and slots for aligning the segments on substantially the same plane. The end caps have wire isolation features, including hooks, shelves and ledges, for separating the interconnect wires routed on the stator to electrically interconnect the segments. The segments include scalloped contours on their outer edges for draining oil, and the end caps have passages for draining oil.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a divisional of U.S. application Ser. No. 10/806,560filed Mar. 23, 2004, the entire disclosure of which is incorporatedherein by reference.

FIELD OF THE PRESENT DISCLOSURE

The subject matter of the present disclosure relates to statorassemblies for electromagnetic machines. More particularly, the subjectmatter of the present disclosure relates to “loose” segmented statorassemblies having discrete and individually wound stator segments andend caps. In one example, the “loose” segmented stator assembly of thepresent disclosure can be used in a hermetic motor of a compressor for arefrigeration system.

BACKGROUND OF THE PRESENT DISCLOSURE

Segmented stators for use in electromagnetic machines, such as hermeticcompressor motors of a refrigeration system, are known in the art. Thesegmented stator assemblies typically include a plurality of segmentsthat form the stator of the motor. The stator is typically containedwithin a shell, and a rotor and shaft are positioned for rotation withina bore of the stator. Each segment of the stator includes a yoke portionand a tooth portion. As is known in the art of electromagnetic machines,such as induction motors, brushless permanent magnet (BPM) motors, andswitched reluctance (SR) motors, the stator teeth are wound with magnetwires to form winding coils having a plurality of phases.

End caps fit on the ends of segments of a stator to facilitate theplacement of wire on the segments. For example, U.S. Pat. No. 6,584,813to Peachee et al. and entitled “Washing machine including a segmentedstator switched reluctance motor,” which is incorporated herein byreference in its entirety, discloses a segmented stator assembly thatuses end caps on the segments. In addition, U.S. Pat. No. 2,688,103 toSheldon; U.S. Pat. No. 2,894,157 to Morrill; U.S. Pat. No. 6,127,753 toYamazaki; U.S. Pat. No. 6,509,665 to Nishiyama et al and U.S. patentapplication Ser. No. 2002/0084716 to Harter et al. disclose variousexamples of end caps for stators. The prior art end caps are typicallyglued to the segments, and winding coils are wound about the toothportions of each segment and on portions of the end caps. Therefore, anyproblems with the end caps can produce poor winding characteristics inthe winding coils, such as undesirable overlap of the winding coils orinefficient density of the winding coils about the tooth portions.

Segmented stators require various manufacturing steps to interconnectall the individually wound coils on the segments to form the phasewindings. To interconnect the winding coils of the stator, it is knownin the art to use a printed circuit board to interconnect the variouswinding coils of the stator. The printed circuit board is generallycircular and has a plurality of terminal pads that connect to terminalpins on each end cap of the stator.

Rather than using a printed circuit board, interconnect wires can beused to connect the various winding coils of opposing electrical phases(voltages). Ends of the interconnect wires can be welded or soldered toterminal pins on the end caps of the stator, such as disclosed in U.S.Pat. No. 2,688,103 to Sheldon. The interconnect wire can be routed onthe stator in several different ways. In one example, the interconnectwires can be routed around the outside portions of the segments. It isknown in the art to provide hooks on the outboard side of a stator forrouting the wires to route interconnect wires on the outside portion ofthe stator. In a compressor motor, however, routing wires on the outsideportion of the stator is not desirable.

In another example, the interconnect wires can be routed within theinside portion of the stator. It is known in the art to use a stitcherring to guide the wires to route interconnect wires on the insideportion of the stator. For example, a stitcher ring, having part no.280138 and manufactured by Emerson Electric Co, is used in motors toroute interconnect wires. The stitcher ring is a disc with a centralopening for passage of a rotor shaft. The stitcher ring positions on alead-end of the stator and fits partially over the bore of the stator. Aplurality of hooks are provided on one side of the stitcher ring and areused to route wire between winding coils. In another example, U.S. Pat.No. 5,900,687 to Kondo et al. discloses an end plate having grooves forarranging the conducting wires between the coils of the various phases.The end plate is fixed onto an upper portion of the winding coils of thestator in the area of the bore.

Because the interconnect wires routed on a stator are positionedadjacent one another, a large voltage differential between the adjacentinterconnect wires can produce phase-on-phase conditions in the motorand can cause premature failure of the insulation on the wires. In acompressor motor, any large voltage differential between adjacent wirescan be magnified because the motor is used as a magnetization fixturewhere upwards of 1600 Volts and 1200 Amps may be passed through thestator at a given instant. In addition, a compressor motor can be usedwith a Pulse Width Modulated (PWM) drive. The waveform from the PWMdrive may have high voltage spikes on the leading and trailing edges ofthe waveform, creating the need to separate the phase wires.Traditionally, motors use insulation made of MYLAR® or NOMEX® betweenthe magnetic wires forming the separate winding coils. It is also knownin the art to use secondary insulation between the interconnect wiresinterconnecting the winding coils. Unfortunately, such secondaryinsulation can increase the manufacturing costs and production time ofthe motor.

Some segmented stator assemblies use interlocking features or hinges onthe segments to hold them together. For example, U.S. Pat. No. 6,127,753to Yamazaki et al. discloses segments having hinged ends that connectadjacent segments together. Unlike the segmented stators havinginterlocking segments, some prior art segments for stators are notformed to directly interlock with other segments of the stator. Instead,such segments have ridged and slotted ends. The ends merely fit togetheron adjacent segments so that the segments are not physically heldtogether in the absence of some other retaining structure. Hence, thestator segments are used to form a stator of the “loose” segmented type.“Loose” segmented stators typically require a secondary retentiondevice, such as a heavy metal band, to hold the segments together whenthe segments are formed into the annular shape of the stator. The heavyband is positioned around the outside diameter of the segments to holdthem together when manufacturing the motor or when transporting thestator as a separate part to customers. In addition, conventionalsegmented stators do not provide a ready way to axially align thesegments to prevent unacceptable differences in tolerances duringmanufacture. Currently, no form of axial alignment for “loose” segmentedstators is thought to exist in the art.

As noted above, segmented stators can be used in hermetic motors for acompressor of a refrigeration system. The compressor has an oil pump onthe bottom of the compressor, which is known as the oil sump. Typically,oil is pumped up through a shaft of the hermetic motor, past the statorand rotor, and to the main bearing of the compressor. From the bearing,the oil is let loose on a lead end of the motor to drain back to the oilsump. The contours of the motor, such as the contours of the segmentedstator, can determine how the oil is allowed to return to the oil sumpfrom the lead end of the motor. In addition, oil from the oil sump inthe hermetic motor can also pool in cavities and recesses of typical endcaps, which can prevent the return of oil to the oil sump. If the motordoes not have sufficient drain area, for example, the oil will becomedammed on the lead-end of the motor. The damming of oil can cause higheroil circulation in the refrigeration system, can starve the oil pump ofoil, and can hinder the performance of the compressor. On the otherhand, if the motor has too much drain area for the return of the oil,then the stator may have less back iron than desired. A stator with lessback iron can have higher magnetic flux saturation and reducedperformance.

Typical stators for hermetic motors in compressors have flat areasdefined on the outside diameter of the stator. The flat areas of thestator provide a drain area for the oil to pass from the lead-end of themotor to the oil sump. In some stators, the flat areas are made verylarge so that the material used to form the stator can be usedefficiently. However, the large size of these flat areas in the statorcan deform the shell of the motor. For example, the progression of thelaminations forming the stator with the flat areas can create issueswith shell deformation. In addition, the scroll shear pattern when usedin a compressor can create issues with shell deformation because of thephysical size of the flat areas on the outside of the stator. Thus, atrade off is typically made between the size of the flat areas in thestator and the efficient use of material used to make the stator.

The subject matter of the present disclosure is directed to overcoming,or at least reducing the effects of, one or more of the problems setforth above.

SUMMARY OF THE PRESENT DISCLOSURE

A stator for an electromagnetic machine includes a plurality of discreteand individually wound stator segments having end caps positioned on thesegments. In one aspect, the end caps have legs for positioning the endcap on the segments with an interference fit. In another aspect, the endcaps have angled surfaces to facilitate winding of wire on the segments.In another aspect, the end caps have male and female couplings that matetogether to couple adjacent segments together. In yet another aspect,the end caps have fingers and slots for aligning the segments onsubstantially the same plane. In a further aspect, the end caps havewire isolation features, including hooks, shelves and ledges, forseparating the interconnect wires routed on the stator to electricallyinterconnect the segments. In another aspect, the segments includescalloped contours on their outer edges for draining oil, and the endcaps have passages for draining oil.

The foregoing summary is not intended to summarize each potentialembodiment or every aspect of the present disclosure.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing summary, preferred embodiments, and other aspects ofsubject matter of the present disclosure will be best understood withreference to a detailed description of specific embodiments, whichfollows, when read in conjunction with the accompanying drawings, inwhich:

FIG. 1 illustrates a plan view of an embodiment of a segmented statorassembly according to certain teachings of the present disclosurepositioned in a shell.

FIGS. 2A through 2B illustrate top and bottom perspective views of thedisclosed segmented stator assembly.

FIGS. 3A through 3B illustrate a plan view and a perspective view of alaminated segment for the disclosed segmented stator assembly.

FIG. 4 illustrates a detailed plan view of a portion of the disclosedsegmented stator assembly.

FIGS. 5A through 5D illustrate various views of an embodiment of a leadend cap on a segment of the disclosed stator assembly.

FIGS. 6A through 6F illustrate various isolated views of the lead endcap for the disclosed stator assembly.

FIGS. 7A through 7C illustrate an alternative embodiment for couplingends of adjacent lead end caps together.

FIGS. 8A and 8B illustrate another alternative embodiment for couplingends of adjacent lead end caps together.

FIGS. 9A through 9C illustrate various views of an embodiment of a baseend cap on a segment of the disclosed stator assembly.

FIGS. 10A through 10F illustrate various isolated views of the base endcap for the disclosed stator assembly.

FIG. 11 illustrates the disclosed lead and base end caps on adjacentsegments having different stack heights.

FIGS. 12A through 12D illustrates an exemplary stitching pattern for theinterconnect wires on the disclosed stator assembly.

FIG. 13 schematically illustrates flux density paths on an example ofthe disclosed stator assembly.

FIG. 14 illustrates a plan view of the disclosed segment relative to acircumference of a shell.

While the disclosed end caps, segments, stator, and associated methodsare susceptible to various modifications and alternative forms, specificembodiments thereof have been shown by way of example in the drawingsand are herein described in detail. The figures and written descriptionare not intended to limit the scope of the inventive concepts in anymanner. Rather, the figures and written description are provided toillustrate the inventive concepts to a person skilled in the art byreference to particular embodiments, as required by 35 U.S.C. § 112.

DETAILED DESCRIPTION A. Stator Assembly

Referring to FIGS. 1 and 2A-2B, an embodiment of a segmented statorassembly 10 according to certain teachings of the present disclosure isillustrated. FIG. 1 illustrates a plan view of the disclosed statorassembly from the lead-end, and FIGS. 2A and 2B illustrate perspectiveviews of the disclosed stator assembly 10 from the lead-end and thebase-end, respectively. The disclosed stator assembly 10 is of the“loose” segmented stator type. The disclosed stator assembly 10 can beused in variable speed motor applications, such as a hermetic compressorfor a refrigeration system of a vehicle or a residence, for example.However, certain teachings of the present disclosure can be used withother types of stator and used in other motor applications.

The segmented stator assembly 10 includes a plurality of discrete statorsegments 20. The segments 20 have lead end caps 50 and base end caps150. In the present example, the segmented stator assembly 10 has ninesegments 20 that are individually wound with wire to form winding coils92, although alternate embodiments with a different number of segmentsand end caps are envisioned and possible. The segmented stator assembly10 is typically contained within a motor shell (not shown), and a rotorand shaft (not shown) are positioned for rotation within a bore 11 ofthe stator 10.

B. Segments

Referring to FIGS. 3A-3B, a laminated segment 20 for the disclosedstator assembly 10 is shown in a plan view and a perspective view,respectively. The construction of each segment 20 is generally similarto the construction of segments used in conventional segmented stators.For example, each segment 20 is formed from a plurality of substantiallyidentical laminations 21. The laminations 21 are made of stamped steeland stacked together to form the segment 20.

Each segment 20 includes a yoke portion 22 and a tooth portion 24. Theyoke portion 22 has an outboard edge 30 that defines a rear channel 38.The rear channel 38 receives a portion of the end caps 50 and 150 in apress-fit relationship to help couple the end caps 50 and 150 to thestator segments 20, which is described in more detail below.

In the present embodiment, each segment 20 includes a slotted end 32 anda ridged end 34 defined in the yoke portion 22. The slotted and ridgedends 32 and 34 of adjacent segments 20 interfit with one another whenthe segments 20 are formed into the annular shape of the stator 10, asbest shown in FIGS. 1 and 2A-2B. In particular, the slotted ends 32receive the ridged ends 34 when adjacent stator segments 20 are broughttogether. The adjacent ends 32 and 34 inhibit relative movement of theadjacent stator segments 20 in at least one direction. Unlike prior artstator assemblies having interlocking hinges or puzzle pieces that serveto directly connect adjacent stator pieces together, the slotted andridged ends 32 and 34 of the present embodiment do not physically holdtogether adjacent stator segments 20 in the absence of some otherretaining structure. Hence, the stator segments 20 in the presentembodiment form a stator of the “loose” segmented type.

In the present embodiment, the tooth portion 24 of the segment 20 has apole end 26, which is generally “T” shaped. The inboard face of the poleend 26 (i.e., the surface of the pole end 26 facing away from the yokeportion 22) forms the bore of the assembled stator within which therotor is positioned for rotation. As is known in the art, wire (notshown) is wound about the tooth portion 24 of the stator segments 20 toform a winding coil. The outboard face of the pole end 26 (i.e., thesurface of the pole end 26 facing the yoke portion 22) at leastpartially helps to position and retain the winding coil in a desiredposition on the tooth portion 24, as described in more detail below.

C. Lead End Caps

As noted above, each of the discrete stator segments 20 of the assembledsegmented stator 10 as shown in FIGS. 1 and 2A-2B has a lead end cap 50and a base end cap 150. Referring to FIGS. 5A-5D, a discrete statorsegment 20 having end caps 50, 150 is shown in a number of isolatedviews to reveal relevant details of the lead end cap 50 for thedisclosed stator assembly. The lead end cap 50 is used on the lead-endof the stator segment 20 (i.e., the end of the stator segment 20positioned toward the main bearing or “top” of the motor). The lead endcap 50 is composed of non-conductive material and is preferably composedof RYNITE® FR530 by Dupont.

The lead end cap 50, which is also shown in various isolated views inFIGS. 6A-6F, includes a body portion 60, a winding portion 74, and aninboard wall 76. The lead end cap 50 fits on the stator segment 20 sothat a substantially flat surface 52 of the end cap 50 positionsadjacent the lead-end of the segment 20. In particular, the body portion60 positions onto the yoke portion 22 of the segment 20, the windingportion 74 positions on to the tooth portion 24 of the segment 20, andthe inboard wall 76 positions of the pole end 26 of the segment 20. Asbest shown in the side views of FIGS. 6D and 6F, both the body portion60 and inboard wall 76 of the lead end cap 50 extend well beyond thewinding portion 74 and form a winding pocket 70, and both the bodyportion 60 and inboard wall 76 have substantially the same height abovethe tooth portion. As schematically shown in FIGS. 5A-5D, wire of thewinding coil 92 is wound within the winding pocket 70 about the toothportion 24 so that a portion of the winding coil 92 is partiallypositioned between the body portion 60 and the inboard wall 76 and ispartially positioned on the winding portion 74 of the end cap 50.

As best shown in FIG. 6A, the winding portion 74 of the lead end cap 50defines a plurality of ribs, which are partly necessary for molding theend cap 50. Preferably, the winding portion 74 defines five ribs forproviding sufficient strength to the end cap 50. The ribs may be formedin the winding pocket 70 where wire is intended to be wound, as shown inFIG. 6A. In an alternative embodiment, the bottom surface 52 (shown inFIG. 6B) may instead define the plurality of ribs. Forming the ribs inthe bottom surface 52 may be beneficial in strengthening the end cap 50because the ribs will be under compression when positioned against thesurface of a segment. In addition, the connection of the winding portion74 with the inboard wall 76 on the top surface of the winding portion 74may be a high stress point. By forming the ribs in the bottom surface 52of the winding portion 74, the potentially “high stress” connection ofthe winding portion 74 to the inboard wall 76 will be uniform, which canreduce the chances of breakage between the winding portion 74 with theinboard wall 76.

1. Retaining Features

As best shown in FIGS. 5A-5D, the lead end cap 50 positions on thestator segment 20 with a plurality of legs. In the present embodiment,the lead end cap 50 includes two tooth legs 82 and a body leg 88. Thetooth legs 82 are attached to the inboard wall 76, the body leg 88 isattached to the edge of the body portion 60, and the legs 82 and 88extend from the flat surface 52 of the end cap 50 for fitting on thesegment 20. When the end cap 50 is positioned on the segment 20, thetooth legs 82 fit on either side of the tooth portion 24, and the bodyleg 88 fits in the channel 38 formed on the outboard edge 30 of thesegment 20. The edges of the tooth legs 82 fit on either side of thetooth portion 24 an interference fit, and an outboard surface of thetooth legs 82 position against the inboard face of the pole end 26.

The three legs 82 and 88 substantially hold the end cap 50 on thesegment 20 and sufficiently align the end cap 50 on the segment 20. Withthe end cap 50 substantially stabilized on the segment 20 by the legs 82and 88, the end cap 50 is prevented from moving during windingprocedures or other manufacturing steps. For example, the legs 82 and 88minimize any axial and tangential movement of the end cap 50 andeliminate the need to glue the end cap 20 to the segment 20.Conventionally, end caps known in the art are glued on the segment tokeep the end cap from moving side to side or into the bore duringmanufacture. On the disclosed end cap 50, however, the tooth legs 82 andthe body leg substantially hold the end caps 50 in place on the segment20 without the need for glue.

2. Undercut Areas

Because the legs 82 and 88 of the lead end cap 50 have edges that forman interference fit with the segment 20, the edges pass against edges ofthe stator segment 20 as the end cap 50 is positioned on the segment 20.Consequently, the edges of the segment 20 can scrape material of theplastic legs 82 and 88 as the end cap 50 is positioned on the segment 20and can force skived material against the flat surface 52 of the end cap50. Any skived material collected between the surface 52 and the segment20 can prevent the end cap 50 from fitting properly flat against thelead-end of the segment 20. Accordingly, the disclosed end cap 50, asbest shown in the bottom view of FIG. 6B, defines under-cut channels 54on the flat surface 52 adjacent the tooth legs 82 and adjacent the bodyleg 88. These under-cut channels 54 collect any skived material from thelegs 82 and 88 when the end cap 50 is fit onto the segment so that theflat surface 52 of the end cap 50 can fit snugly against the lead-end ofthe segment.

As also shown in the bottom view of FIG. 6B, the flat surface 52 of thelead end cap 50 defines a divot 57 to accommodate an interlock tab(element 37 shown in FIG. 3A) that is conventionally used for stackinglaminations of the segment. Furthermore, the outboard edge of the bodyportion 60 defines passages 67 that also accommodate the other interlocktabs (elements 37 shown in FIG. 3A) on the segment. As best shown inFIG. 6B, the passages 67 on the lead end cap 50 communicate a hollow 61of the body portion 60 with the outboard edge of the end cap 50 so thatthe passages 67 also serve as drain holes, as described in more detailbelow.

-   -   3. Pocket Features

In the present embodiment and as best shown in the detailed view of FIG.4, the lead end caps 50 each preferably include first and second pockets68+ and 68− for insulation displacement connectors (IDCs) (not shown).The IDC pockets 68+ and 68− each have an inboard slit 69-I and anoutboard slit 69-O. A leading portion 93L of the wire used to form thewinding coil 92 fits in one of the IDC pockets 68+, and the trailing end93T of the wire 90 of the winding coil 92 fits in the other IDC pocket68−. In an exemplary interconnect scheme described in more detail below,a phase interconnect wire 94A used to interconnect the winding coilsbetween segments 20 of the same phase also fits into the one IDC pocket68+ on the end cap 50. In the exemplary interconnect scheme, a neutralor common interconnect wire 96 used to interconnect the common ends ofthe winding coils 92 of the stator fit into the other IDC pocket 68−.Thus, the slits 69-I, 69-O pass the wires 90, 94, 96 through the IDCpockets 68+, 68− between the inboard and the outboard sides of thestator assembly 10.

As best shown in FIGS. 5A-5D, the lead end cap 50 positions on thestator segment 20 with a plurality of legs. In the present embodiment,the lead end cap 50 includes two tooth legs 82 and a body leg 88. Thetooth legs 82 are attached to the inboard wall 76, the body leg 88 isattached to the edge of the body portion 60, and the legs 82 and 88extend from the flat surface 52 of the end cap 50 for fitting on thesegment 20. When the end cap 50 is positioned on the segment 20, thetooth legs 82 fit on either side of the tooth portion 24, and the bodyleg 88 fits in the channel 38 formed on the outboard edge 30 of thesegment 20. The edges of the tooth legs 82 fit on either side of thetooth portion 24 with an interference fit, and an inboard surface of thetooth legs 82 position against the outboard face of the pole end 26.

The inboard slit 69-I of the IDC pockets 68+, 68− are specificallypositioned to ensure that the wire 90 that forms the winding coil 92 ispositioned in a defined relationship to the tooth portion 24 of thesegment 20. In particular and as best shown in FIG. 6A, the inboard slit69-I of the IDC pockets 68+ is substantially aligned with the edge ofthe winding portion (not shown) that fits adjacent the tooth portion 24of the segment 20. A groove 65 is preferably formed in the body portion60 of the end cap 50 from the slit 69-O to the edge of the windingportion 74. As best shown in FIG. 4, the groove 65 is used to guide andhide the leading portion 93L for the winding coil 92 to the toothportion of the segment. On the other hand and as best shown in FIG. 6A,the inboard slit 69-I of the other IDC pockets 68− is positioned furtherfrom the edge of the winding portion 74. As best shown in FIG. 4, theinboard slit 69-I of the other IDC pockets 68− receives the trailingportion 93T of the winding coil 92.

In addition to the slits 69-I, 69-O, the lead end cap 50 includes aconnection reference walls 140 on an inboard side of the body portion60, as best shown in FIG. 4. The connection reference wall 140 ispositioned away from IDC pockets 68+, 68− and is used to align wire withthe slits 69-I, 69-O when positioning the wire on the stator 10 duringmanufacture. Edges 142 of the wall 140 are substantially aligned withthe inboard slits 69-I and are used to bend wire relative to the inboardslits 69-I. The connection reference wall 140 also has tips or portions144 that extend beyond the body portion 60. The tips 144 create areference point for aligning the wire in the slits 69-I, 69-O of the IDCpockets 68+, 68−. For example, the tips 144 of the wall 140 extends farenough beyond the body portion 60 to allow a winding probe or nozzle tobend the wire above the IDC pocket 68+, 68− before the wire is put intothe slits 69-I, 69-O. Having the extending tips 144 of the wall 140eliminates the need to have a hook extending above the body portion 60,which could interfere with an automated winding process.

As best shown in FIG. 4, the lead end cap 50 also has alignment slots146 adjacent each of the IDC pockets 68+, 68−. The alignment slots 146facilitate automated assembly of the stator 10 by providing a referencepoint for aligning automated devices that embed IDCs (not shown) in theIDC pockets 68+, 68−. For example, the present embodiment preferablyuses insulation displacement connectors (IDCs) manufactured by Tyco. TheIDCs fit into the pockets 68+, 68−. Preferrably, the IDC pockets 68+,68− have upward posts within the pockets to facilitate positioning ofthe IDCs. Once installed, the IDCs electrically connect the winding coilwires (e.g., 92) and the interconnect wires (e.g., 94A and 96) passingthrough the pocket 68+, 68−. In addition, the IDCs provide a terminalfor a wire lead to connect to the motor. The end cap 50 also includes amounting hole 66 in which a cable tie for holding the wire lead can besnapped.

D. Base End Caps

As noted above, the discrete segments 20 of the stator 10 have base endcaps 150. Referring to FIGS. 9A through 9C, a stator segment 20 havingend caps 50, 150 is shown in a number of isolated views to revealrelevant details of the base end caps 150 for the disclosed statorassembly. The base end cap 150 is used on the base end of the statorsegment 20 (i.e., the end of the stator segment positioned toward theoil sump or “bottom” of the motor). The base end cap 150 issubstantially similar to the lead end cap discussed above. For example,the base end cap 150, which is shown in a number of isolated views inFIGS. 10A through 10F, includes a body portion 160, a winding portion174, an inboard wall 176, and a substantially flat surface 152.

The base end cap 150 fits on the base-end of the stator segment 20 in asimilar fashion to the fitting of the lead end cap on the lead-end. Forexample, the base end cap 150 has two tooth legs 182 attached to theinboard wall 176 and extending from the flat surface 152. The disclosedend cap 150 also has a body leg 188 attached to the body portion 160 andextending from the bottom surface 152. When positioned on the segment20, the tooth legs 182 of the base end cap 150 fit one either side ofthe tooth portion and against the pole end 26 with an interference fit,and the body leg 188 fits in the channel 38 formed on the outboard edge30 of the segment 20. The legs 182 and 188 securely hold the base endcap 150 on the segment 20, thus not allowing the end cap 150 to moveduring winding procedures or other manufacturing steps.

Similar to the lead end cap discussed above, the base end cap 150, asbest shown in the top view of FIG. 10A, includes under-cut channels 154on the flat surface 152 adjacent the legs 182 and 188 for collectingskived material from the legs 182 and 188 when the base end cap 150 ispositioned onto a segment. Furthermore, the flat surface 152 of the baseend cap 150 defines a divot 157, and the edge of the body portion 60defines nooks 167 to accommodate the interlock tabs (elements 37 in FIG.3A) conventionally used for stacking laminations of a segment.

E. Winding Procedure

During assembly of the disclosed stator 10, the segments 20 are formedfrom a plurality of stacked laminations in a process known in the art,such as shown in FIGS. 3A and 3B, for example. Then, the lead and baseend caps 50 and 150 are positioned on the discrete segment 20. Next,strips of MYLAR® or other such material (not shown) are attached to thesides of the tooth portions 24 of the segments 20, as known in the art.The strips typically have an adhesive backing for attachment and provideprotection and insulation for wire to be wound on the tooth portion 24.Then, a winding coil 92, which is schematically shown in FIGS. 5C and5D, for example, is formed on the segment 20. The windings coils 92 areformed by techniques known in the art, such as fly or needle winding.Preferably, the present embodiment uses a winding technique having aspindle and bobbin where a winding coil 92 is individually wound abouteach discrete stator segment 20.

In the present embodiment, one of benefits of the “loose” segmentedstator is that the discrete stator segments 20 can be freely handled andcan be individually rotated to wind with wire to form the winding coil.Thus, access to the slot area of the discrete stator segments 20enhances precision in the winding procedure and offers denser slotfills. In addition, the access to the discrete segment 20 allows thesegments 20 to be wound at high speeds.

Briefly, the spindle/bobbin winding technique begins by placing thesegment 20 having the attached insulation strips and end caps 50, 150 inan arbor machine that latches onto the ends 32 and 34 of the segment 20.A leading portion of wire is bent about the projecting post 148 on theoutboard side of the lead end cap 50 to position the wire in a fixedlocation on the end cap 50. The wire is then inserted into the slits 69of the IDC pocket 68+. The arbor machine rotates the segment 20, and amovable wire nozzle feeds wire to the segment 20. While the segment 20is rotated, the wire is wound about the tooth portion 24 of the segment20 and the winding portions 74, 174 of the end caps 50, 150 to form thewinding coil 92.

At completion of the coil 92, the wire is then run out towards theoutboard side of the end cap 50 through the slits 69 of the neutral IDCpocket 68− on the lead end cap 50 where the wire is then trimmed.Preferably, the wire is bent at an angle from the outboard slit 69-O toprevent the wire from coming out of the pocket 68− after trimming. Asthose of skilled in the art will appreciate, winding a coil about atooth portion 24 of a segment 20 in a given direction achieves anelectromagnet of a polarity when the winding is energized in that givendirection. Such a winding process is repeated individually on thevarious segments 20 for the stator.

As schematically shown in FIGS. 5C and 5D, wire of the winding coil 92is wound so that portions of the winding coil 92 are also partiallypositioned between the body portions 60, 160 and the inboard walls 76,176 of the end caps 50, 150. The wire of the winding coil 92 is alsowound so that portions of the coil 92 are partially positioned betweenthe legs 82, 182 and the yoke portion 22 of the segment 20. The distalends of opposing legs 82 and 182 on the lead and base end caps 50 and150 preferably substantially meet one another so as to not allow metalof the pole end 26 to be substantially exposed, as best shown in FIGS.5C and 5D. Thus, the legs 82 and 182 add substantial insulation for thewinding coil 92 from the metal that forms the pole end 26 of thesegments 20.

To facilitate winding of the wire during the winding procedure, the leadend cap 50, as best shown in the side views of FIGS. 6D and 6F, has awinding pocket 70 that gives a substantially constant slot dimensionabout the end cap 50 and tooth portion (not shown) of a segment whenpositioned thereon. The body portion 60 on the lead end cap 50 has aninboard side that is substantially perpendicular to the winding portion74 that fits onto the tooth portion of the segment. The inboard wall 76has an outboard side that is substantially perpendicular to the windingportion 74 and that opposes the inboard side of the body portion 60.

An angled surface 75 of the end cap 50 angles from the winding portion74 to the inboard side of the outboard wall 76. The angled surface 75 isconfigured to position wire of the winding coil (not shown) in the slotarea between the body portion 60 and inboard wall 76. Furthermore, thetooth legs 82 each have an angled surface 85 on an outboard side of thelegs 82. The angled surface 85 angles from a side of the tooth portion(not shown) of the segment. This angled surface 85 is similarlyconfigured to position wire of the winding coil in the slot area betweenthe pole end 26 and the yoke portion 22 of the segments, as shown inFIGS. 5C and 5D, for example.

The wire pocket 70 of the end cap 50 is contoured to have substantiallythe same cross-sectional slot area in both the axial and circumferentialdirections. As shown in FIG. 6D, the angled surface 75 near the inboardwall 76 defines an angle α₁. As shown in FIG. 6B, the angled surfaces 85on the legs 82 defines an angle α₂. The angle α₁ is preferablysubstantially equivalent to the angle α₂. In addition, these angledsurfaces 75 and 85 preferably transition smoothly where they meet withone another so that the transition between the angled surfaces alsodefine the same angle as angles α₁ and α₂ relative to the tooth portionof the segment. In one embodiment, the angles α₁ and α₂ are about110-degrees.

As shown in FIGS. 3A and 3B, for example, the sides of the tooth portion24 are preferably substantially perpendicular to the lead-end andbase-end of the segment 20. As noted above, the bottom surface 52 of thelead end cap 50 is positioned parallel against the lead-end of thesegment, and the edges of the winding portion 72 are aligned with theedges of the tooth portion of the segment. Because the wire pocket 70 ofthe end cap 50 is contoured to have substantially the samecross-sectional slot area in both the axial and circumferentialdirections. Thus, the wire is given a substantially constant slotdimension as the segment 20 is rotated during a winding procedure. As aresult, the wind of the winding coil on the segment can be performedfaster, tighter, and more consistently. In addition, the wire formingthe winding coil can comfortably fall into place in the wire pocket 70as the wire is layered during the winding procedure and can reduce oreliminate “wire collapse” and cross over of the wire in the coil duringthe winding procedure, which achieves a denser winding coil.

To facilitate winding of the wire during the winding procedure, the baseend cap 150, as best shown in the side views of FIGS. 10D and 10F, alsohas a winding pocket 170 that gives a substantially constant slotdimension about the end cap 150 and tooth portion (not shown) of thesegment when positioned thereon. The winding pocket 170 is substantiallysimilar to that disclosed above for the lead end cap. For example, thebody portion 160 on the base end cap 150 has an inboard side that issubstantially perpendicular to the winding portion 174 that fits ontothe tooth portion of the segment. The inboard wall 176 has an outboardside that is substantially perpendicular to the winding portion 174 andthat opposes the inboard side of the body portion 160. An angled surface175 of the end cap 150 angles from the winding portion 174 to theinboard side of the outboard wall 176 to position wire of the windingcoil. Furthermore, the tooth legs 182 each have an angled surface 185 onan outboard side of the legs 182 to position wire of the winding coil.As with the lead end cap described above, the angled surfaces 175 and185 are similarly configured to position wire, and each surface 175 and185 defines a substantially equivalent angle with respect to the toothportion.

F. Mechanical Assembly of Stator

After the segments 20 are individually wound according to certainteachings of the present disclosure detailed herein, the individuallywound segments 20 are assembled into a generally annular configurationto form the stator. As noted in the Background Section of the presentdisclosure, some segmented stator assemblies use interlocking featuresor hinges on the segments to hold them together. In another type ofsegmented stator assembly, co-pending U.S. patent application Ser. No.10/427,450, entitled “Segmented Stator With Improved Handling AndWinding Characteristics And Method Of Winding The Same” and filed Apr.30, 2003, which is incorporated herein by reference in its entirety,discloses a segmented stator assembly that uses flexible containmentstructures on the segments to hold them together. In contrast, thestator segments 20 of the present embodiment preferably have the ridgedand slotted ends 32 and 34 that are positioned into physical contactwith one another to form a closed magnetic circuit, and no direct,segment-to-segment attachment exists between the stator segments 20.

1. Coupling between End Caps

As noted in the Background Section of the present disclosure, typical“loose” segmented stators (e.g., those stators with segments that do notinterlock together by a hinge) need a heavy band that is typically madeof metal to be placed around the outside of the segments to hold thesegments together, especially during the manufacturing process. In thepresent embodiment, however, respective ends 62/64 and 162/164 of thedisclosed end caps 50 and 150 couple together to interconnect orsubstantially hold the individually wound stator segments 20 together.The respective ends 62/64 and 162/164 of the disclosed end caps 50 and150 can be coupled together by hand or by automation. On the lead endcap 50 best shown in FIGS. 5A-5D, one end 62 of the end cap body portion60 preferably includes a male coupling 62, and another end 64 preferablyincludes a female coupling 64. The male and female coupling 62 and 64are preferably features incorporated into the body portion 60 of the endcap 50. The male coupling 62 preferably extends from the end of the bodyportion 60 adjacent a slotted end 32 of the yoke portion 22 of thesegment 20. In addition, the female coupling 64 is preferably defined inthe end of the body portion 60 positioning adjacent the ridged end 32 ofthe yoke portion 22.

These male and female couplings 62 and 64 mate together between adjacentend caps 50 to substantially hold the segments 20 together, as bestshown in FIG. 4, for example. In the present embodiment, the male andfemale couplings 62 and 64 are snap features. The male coupling 62includes deformable, bifurcate catches, and the female coupling 64includes a grooved slot. When the pressed into the female coupling 64,teeth on the ends of the bifurcate catches 62 engage inside the groovesof the female coupling 64. The male and female couplings 62 and 64eliminate the need for a heavy metal band or any other special fixtureto independently hold the segments together during manufacturing orduring transportation of the assembled stator.

In alternative embodiment illustrated in FIGS. 7A and 7B, ends 62′ and64 of adjacent end caps 50, 50′ can couple together using a separateC-clamp 100. The ends 62′, 64 of the adjacent end caps 50, 50′ can eachdefine a pocket 102. The separate C-clamp 100, which can be stainlesssteel, for example, can fit within the pockets 102 of the adjacent endcaps 50, 50′ to couple them together. The pockets 102 can each include aretaining rib 103 formed on the inner wall of the cavity 61 of the endcaps 50, 50′. The retaining ribs 103 can engage the C-clamp 100 and canhold it in place. In contrast to the retaining ribs 103 and as shown inFIG. 7B, the pockets 102 can each include a retaining slot 103′ formedon the inner wall of the cavity 61 of the end caps 50, 50′. The C-clamp100′ can have hooked ends that can fit within the retaining slots 103′to hold the clamp 100′ in place. The slots 103′ can be elongated alongthe height of the end caps 50, 50′ to allow for adjustment between theadjacent end caps 50, 50′ due to differences in tolerances from thelaminated segments 20, 20′ and end caps 50, 50′.

In another alternative embodiment illustrated in FIGS. 8A and 8B, ends62′, 64 of the adjacent end caps 50, 50′ can couple together using aseparate cotter pin 104. One end 62′ of an adjacent end cap 50′ caninclude a stem 107 that extends from the side of the end cap 50′ andthat has a retaining hole 108. The other end 64 of the adjacent end cap50 can define a hole 105 in which the cotter pin 104 inserts. The stem107 on the one end cap 50′ can fit into an opening 106 in the sidewallof the adjacent end cap 50. The cotter pin 104 can then be fit throughthe hole 105 of the end cap 50, and the end of the cotter pin canconnect into the hole 108 in the stem 107. In this way, the cotter pin104 and stem 107 can substantially hold the adjacent end caps 50, 50′together. Moreover, the opening 106 in the sidewall through which thestem 107 inserts can be elongated along the height of the end caps 50,50′ to allow for adjustment between the adjacent end caps 50, 50′.

2. Alignment Features

As best shown in FIGS. 9A through 9C, the base end cap 150 similarly hasends 162 and 164 that mate together to hold adjacent segments 20together. The ends 162 and 164 in the present embodiment aresubstantially similar to those on the lead end cap described above. Inaddition to the mating ends 162 and 164, the base end cap 150 has afeature for aligning adjacent segments 20. The alignment featureincludes an alignment slot 192 on one end of the body portion 160 andincludes an alignment finger 194 on another end.

Preferably, the finger 194 extends from the end of the body portion 160having the female coupling 164. The finger 194 extends from the bodyportion 60 for inserting into the slot 192 of an adjacent base end cap150. As best shown in FIG. 10C, the alignment finger 194 has a side 195that is substantially on the same plane as the substantially flatsurface 152 of the end cap 150. When the base end cap 150 is positionedon a segment, the side 195 of the finger 194 lies on substantially thesame plane as the base-end of the segment. Preferably, the slot 192 isdefined in the same side of the body portion 160 having the malecoupling 162. As best shown in FIG. 10A, the alignment slot 192 is opentoward the end of the end cap 150 for inserting a finger 194 of anadjacent base end cap 150. In addition, the alignment slot 192 has anopen side 193 towards the flat surface 152 of the base end cap 150. Whenthe base end cap 150 is positioned on a segment, the open side 193 ofthe slot 192 exposes the base-end of the segment.

Referring to FIG. 11, lead and base end caps 50 and 150 are showncoupled together on adjacent segments 20 of an assembled stator. The endcaps 50, 150 on the various segments 20 of the stator may have differenttolerance values. In addition, the stack heights of the various segments20 can vary as much as plus or minus two (2) lamination thicknesses perstack, which can be caused by variations in the plurality of laminationsused to form the segments 20. Differences in tolerances and stackheights can create unevenness in the axial direction A (e.g., thedirection generally parallel to a central axis of the assembled stator)when the various segments 20 are put together to assemble the stator.For illustrative purposes, the adjacent segments 20 in FIG. 11 are shownwith different stack heights SH₁ and SH₂.

The disclosed end caps 50 and 150 have features to overcome differencesin tolerances and stack heights. When the base end caps 150 of theadjacent segments 20 are brought together, the finger 194 on one end cap150 fits within the slot 192 on the adjacent end cap 150. The end of thefinger 194 is preferably chamfered as shown because the finger 194inserts into the slot 192. When positioned in the slot 192, the side 195of the finger 194 positions against the substantially flat, base surface28 of the adjacent segment 20 exposed by the open side (not labeled) ofthe slot 192. As a result, the substantially flat, base surfaces 28 ofthe adjacent segments 20 lie substantially on the same plane P.

In addition, the male and female couplings 62,64 and 162,164 can adjustrelative to one another in the axial direction A when the end caps 50and 150 are mated together. In particular and as best shown in FIGS.5A-5D or 9A-9C, the male and female couplings 62,64 and 162,164 areformed substantially along the height of the end caps 50 and 150, andthe female couplings 64 and 164 are open ended in the axial direction.Thus, the male and female couplings 62,64 and 162,164 can adjustrelative to one another in the axial direction once mated together toaccommodate for differences in tolerances and stack heights between thevarious segments 20 and end caps 50, 150 of the stator when assembled.

Furthermore, the male and female couplings 62 and 64 on the lead endcaps 50 preferably do not extend to the substantially flat surface onthe bottom of the lead end cap 50, as shown in FIG. 11 and also in FIGS.6B-6F. In this way, undercuts, generally indicated as 63, are formedbeneath the couplings 62 and 64. With the adjacent segments 20 and leadend caps 50 coupled together as shown in FIG. 11, these undercuts 63provide space for any differences in tolerances or stack height betweenthe adjacent segments 20. Thus, if one segment 20 has a greater stackheight SH₁ than the stack height SH₂ of the adjacent segment 20, thecoupling 62 or 64 on the adjacent end cap 50 will not contact the top ofthe greater stacked segment 20. Instead, the undercut 63 willaccommodate any excess stack height on the greater stacked segment 20.

These features of the disclosed end caps 50 and 150 can reduce theeffects of certain problems associated with a segmented stator. In oneexemplary problem, unevenness in the segmented stator can cause problemswhen a shell is pressed on the stator during manufacture. The shell mayhit certain segments 20 first, causing the segments 20 to possibly pullaway from each other or possibly forcing the shell to be improperlypressed on the stator. The alignment slots 192 and fingers 194 on thebase end caps 150 provide the assembled stator with a substantiallylevel base for holding the stator when pushing a shell over the stator.In another exemplary problem associated with a segmented stator,tolerance values of the various components of the stator, motor, andcompressor can accumulate during manufacture. Aligning the base end cap150 and base surfaces 28 of the segments 20 with the alignment slots 192and fingers 194 provides a reference point for tolerances. In this way,the manufacturer can better accommodate or control the stacking oftolerance values when building the stator, motor, and compressor.

Furthermore, aligning the base end cap 150 and base surfaces 28 of thesegments 20 can reduce unevenness in the segmented stator that can causeproblems when the motor is stitched with interconnect wire, as describedbelow. As alluded to in the Background Section of the presentdisclosure, any unevenness of the segmented stator 10 can cause problemswhen the stator 10 is stitched. An automated stitching device may placea force on each individual laminated segment 20 as the stator ispositioned to perform the interconnections between the segments 20. Ifone of the segments 20 were “up” from the lower supporting datum (e.g.,the base surface of the one segment 20 is above the general plane P ofthe other segments 20), the force of the stitch operation could causethe segment 20 to move and can possibly create a mis-stitch or scrappart. Having the segments 20 lie substantially on one plane P asdiscussed in FIG. 11 and supporting the stator 10 from that plane P or aplane parallel thereto during the stitching operation can substantiallyavoid any of these manufacturing issues. For this reason, the consistentdatum between each of the individual segments 20 provided by thealignment slots and fingers 192 and 194 can be beneficial.

G. Wire Isolation

As noted above in the Background Section of the present disclosure, allthree types of Induction, BPM, or SR motors can have phase-on-phaseissues where adjacent wires of opposing electrical phases produce alarge voltage differential between the adjacent wires. Suchphase-on-phase issues can be aggravated when the motor is used as amagnetization fixture having large voltages and amps passed through thestator at one given instant. In addition, a drive (not shown) operatesto control energization of the winding coils of the stator 10. In oneembodiment, a Pulse Width Modulated (PWM) drive can be used with thedisclosed stator assembly 10. However, other conventional techniques forcontrolling the energization of the winding coils can be used. As notedabove, phase-on-phase issues can be aggravated when a PWM drive is usedto drive the motor, because the waveform from the PWM drive may havehigh voltage spikes on the leading and trailing edges of the wave form,creating a need to separate the phases.

In the present embodiment, conventional insulation is preferably usedbetween adjacent winding coils 92. As noted previously, however, priorart solutions not only use insulation between adjacent winding coils butalso use additional insulation, such as MYLAR® or NOMEX® sheets andtubes, between adjacent interconnect wires to potentially reduce effectsof phase-on-phase issues. Unfortunately, the additional insulationincreases the cost and time of manufacturing the motor. As also notedpreviously, prior art solutions may simply route wire on the outside ofthe stator to interconnect the winding coils of the various phases. Inaddition, prior art solutions may merely use posts on the end caps tobend wire or may use rings with various hooks to route wire between thecoils. Such prior art solutions allow wires of different phases to passnext to each other or even touch, which can produce undesirablephase-on-phase issues.

1. Routing Features on Lead End Caps

In the present embodiment, the lead end cap 50 includes a plurality ofwire isolation features for routing and separating the interconnectwires. In contrast to the prior art, the wire isolation features areintended to substantially eliminate or reduce such phase-on-phase issuesbetween adjacent interconnect wires without the use of additionalinsulation by keeping the interconnect wires of any given phase fromtouching another wire of a different phase or from positioningsubstantially close to another wire of a different phase. In oneexample, the wire isolation features create a minimum of 0.030-inch (onewire diameter) air clearance between adjacent interconnect wires. Inaddition, the wire isolation features on the disclosed end caps 50 aredesigned for automated stitching. In the present embodiment of the leadend cap 50, as shown in FIGS. 5A-6F, the wire isolation features includean inboard router or hook 110, an outboard router or hook 120, andanother inboard router or wall shelf 130 positioned on the disclosed endcap 50.

a. Inboard Hook

As best shown in FIG. 5B, for example, the inboard hook 110 ispositioned on the inboard wall 76 of the lead end cap 50 and extendsfrom one side edge of the inboard wall 74. The inboard hook 110 has ahigh ledge 112, a low ledge 114, and a catch 116. The high ledge 112routes wire a further distance from the segment 20 of the stator, andthe low ledge 114 routes wire a closer distance from the segment 20 ofthe stator. Thus, the high and low ledges 112, 114 on the inboard hook110 separate interconnect wires routed from one portion of the stator toanother. The catch 116 positions the interconnect wires on the ledges112, 114 and can used to bend the interconnect wire.

b. Outboard Hook

As shown in FIG. 5C, for example, the outboard hook 120 is positioned onthe body portion 60 of the lead end cap 50 adjacent one of the IDCpockets 68+. The outboard hook 120 extends beyond the body portion 60and has a high ledge 122 and a low ledge 124. The high ledge 122 routesinterconnect wire a further distance from the segment 20 of the stator,and the low ledge 124 routes interconnect wire a closer distance fromthe segment 20 of the stator. Thus, the high and low ledges 122, 124 onthe outboard hook 120 separate interconnect wires routed from oneportion of the stator to another. The high ledge 122 preferably definesa notch 126 for positioning the wire on the high ledge 122. As notedabove, the end cap 50 is preferably injection molded without the need ofside pulls during the molding process so that the surfaces of the endcap 50 can be formed from two dies that are pulled apart. To form thelow ledge 124 that passes adjacent to the body portion 60, a window 125(shown in FIGS. 6A and 6B) is defined in the body portion 60 adjacentthe low ledges 124. The window 125 communicates with the hollow 61 ofthe body and allows the end cap 50 to be molded without the use of aside pull, which can reduce the time and costs associated withmanufacturing.

c. Wall Shelf

As best shown in FIG. 5A, for example, the wall shelf 130 is positionedon the outboard side of the inboard wall 76. In the present embodiment,the inboard wall 76 is relatively higher than found on existing end capsand is intended to prevent interconnect wire from interfering with therotating rotor (not shown). In addition, the high inboard wall 76 helpsguide the interconnect wires so that they do not touch one another. Thewall shelf 130 includes a high ledge 132 and a low ledge 134 forseparating interconnect wire routed past the inboard wall 76 from oneportion of the stator to another. The high ledge 132 routes interconnectwire a further distance from the segment 20 of the stator, and the lowledge 134 routes interconnect wire a closer distance from the segment 20of the stator. The high ledge 132 is preferably positioned adjacent theinboard hook 110 on the side edge of the inboard wall 76, and the lowledge 134 is preferably positioned adjacent an opposite side end of theinboard wall 76. While winding the phases of the motor, the interconnectwires are able to rest on the wall shelf 130 on the inboard wall 76,which can prevent the interconnect wires from interfacing with the rotorwhile the wire is tightened.

2. Exemplary Stitching Operation

With the individually wound segments 20 fit together, the assembledstator can proceed through the manufacturing processes without the needfor a shell or metal band to hold the segments 20 together. As shown inFIG. 1, a conventional plastic cable tie 12 can be positioned about thestator assembly 10 for temporary retention of the stator assembly duringfurther manufacturing steps.

In a further manufacturing step, the various winding coils of thesegments are interconnected to form a desired phase arrangement of themotor. A number of techniques for connecting the winding coils of asegment stator are known and used in the art. In the present embodiment,however, a stitching process is used to electrically connects theindividual winding coils to form the desired phase pattern. Thestitching process can be done manually or automatically by techniquesknown in the art. Preferably, the stitching process for the disclosedstator 10 is preformed by an automated stitching device for positioninginterconnect wire on the stator to interconnect the winding coils.Details of an automated stitching device and stitching techniques aredisclosed in co-pending U.S. patent application Ser. No. 10/193,515,filed Jul. 11, 2002 and entitled “Improved Interconnection Method forSegmented Stator Electric Machines,” which is incorporated herein byreference in its entirety.

Briefly, the automated stitching device may be similar to conventionalwinding equipment used to wind the individual stator segments, becausethe mechanisms for routing the interconnect wires are substantiallysimilar to those used for winding wire around the segments. Theautomated stitching device is preferably a computer numerical controlled(CNC) machine. The automated stitching device can have a wire nozzle tofeed wire, a stationary or movable spindle to position the wire, and arotating or stationary mount for supporting the stator, for example. Theneedle and/or the stator are moved in a programmable fashion to positioninterconnect wires from end cap to end cap on the stator. For example,the automated stitching device can be moved by a controller and motorarrangement, while the stator is held stationary. On the other hand, theautomated stitching device can be stationary, while the stator ispositioned by a controller and motor arrangement. Alternatively, boththe automated stitching device and the stator can be moved by controllerand motor arrangements.

To avoid phase-on-phase issues, the inboard hooks 110, outboard hooks120, and wall shelves 130 on the lead end caps 50 are used in theautomated stitching operation to connect the various phases of themotor. The automated stitching operation may use a wire nozzle, whichcan have a 4-mm diameter, to position interconnect wire between thevarious end caps 50. Because wire nozzle may require extra spacing forinternal clearances as the nozzle is moved relative to components of thestator 10, the features of the lead end cap 50 preferably provide atleast 4-mm clearance for passage of such a wire nozzle.

In FIGS. 12A through 12D, preferred steps of a stitching operation onthe disclosed stator assembly 10 are schematically illustrated. As shownin FIG. 12A, the present example of the disclosed stator assembly 10 hasnine stator segments that are numbered consecutively in a clockwisedirection. Each segment 20 of the stator 10 is identified with a labelidentifying a phase of a winding coil on the segment 20. The windingcoils are not shown in FIGS. 12A through 12D for clarity. Having ninesegments 20 in the present embodiment, each phase winding A, B, Cincludes a winding coil wound about the tooth portion of three statorsegments 20 that are alternatingly positioned about the stator 10. Thenumber of segments and the number of phases in FIGS. 12A through 12D areonly exemplary, and other arrangements can be used without departingfrom the teachings of the present disclosure.

a. Phase-C Interconnect

When the segments 20 are initially formed into the annular stator 10 asshown in FIG. 12A, the winding coils (not shown) of the phases A, B, Care not electrically connected to one another. A first stitching step toconnect the winding coils for the exemplary stator assembly 10 involvesconnecting the phase C winding coils in a reverse direction (e.g.,counterclockwise in the example). In the Figures that follow, anystitched interconnect wires between steps are not shown for clarity. Inaddition, any excess portion of wire used in the stitching operationthat is eventually removed is also not shown for clarity. In this firststitching step, portion of the phase-C interconnect wire 94C ispositioned through the pocket IDC+ on the end cap for segment S-3. Asnoted above, a leading portion of the winding coil 92 for S-3 is alreadyrouted through pocket IDC+ so that the phase-C interconnect wire and thewire for the winding coil can be electrically connected by an IDC (notshown) that will be positioned in the pocket IDC+ during later stages ofassembly.

From the pocket IDC+ on S-3, the interconnect wire 94C is then routed inthe counterclockwise direction to the low outboard ledge 124 on S-3,past the outboard wall on S-2, to low inboard ledge 114 on S-1, and tolow inboard ledge 114 on S-9. At S-9 having phase C, the interconnectwire 94C is routed around the edge 142 of the connection reference walland positioned through the slits in pocket IDC+. Next, the wire 94C isrouted to low outboard ledge 124 on S-9, past the outboard wall on S-8,to low inboard ledge 114 on S-7, and to low inboard ledge 114 on S-6. AtS-6 also having phase C, the wire 94C is routed around the edge 142 ofthe connection reference wall and positioned through the slits in pocketIDC+. Thus, the phase-C interconnect wire 94C interconnects all of thepockets IDC+ of the segments S-3, S-9, S-6 for phase C. The phase-Cinterconnect wire 94C is eventually trimmed on the outboard sides of theend caps 50 at the outboard slits of pockets IDC+ on S-3 and S-6, andthe stitching procedure continues to the next steps.

b. Phase-B Interconnect

As shown in FIG. 12B, a subsequent stitching step involves connectingphase B in a reverse direction (e.g., counterclockwise in the example).In this stitching step, portion of the phase B interconnect wire 94B ispositioned through pocket IDC+ on the end cap for segment S-2. The wire94B is then routed in the counterclockwise direction to low outboardledge 124 on S-2, past the inboard wall on S-1, to high inboard ledge112 on S-9, and to high inboard ledge 112 on S-8. At S-8 having phase B,the wire 94B is routed around the edge 142 of connection reference walland positioned through the slits in pocket IDC+. Next, the wire isrouted to low outboard ledge 124 on S-8, past the outboard wall on S-7,to high inboard ledge 112 on S-6, and to low inboard ledge 114 on S-5.At S-5 also having phase B, the wire 94B is routed around the edge 142of connection reference wall and positioned through pocket IDC+. Thus,the phase-B interconnect wire 94B interconnects all of the pockets IDC+of the segments S-2, S-8, S-5 for phase B. The interconnect wire 94B iseventually terminated at the outboard slits of pockets IDC+ on S-2 andS-5.

c. Phase-A Interconnect

As shown in FIG. 12C, a next step of the process involves connectingphase A in a reverse direction (e.g., counterclockwise in the example).In the stitching step, portion of the phase A interconnect wire 94A ispositioned through pocket IDC+ on the end cap for segment S-7. Frompocket IDC+, the interconnect wire 94A is routed in the counterclockwisedirection past the inboard wall on S-6, to high inboard ledge 112 onS-5, and to high inboard ledge 112 on S-4. At S-4 having phase A, thewire 94A is routed around the edge 142 of the connection reference walland positioned through the slits in pocket IDC+. Form pocket IDC+, thewire is routed to low outboard ledge 124 on S-4, past the inboard wallon S-3, to high inboard ledge 112 on S-2, and to high inboard ledge 112on S-1. At S-1 also having phase A, the wire 94A is routed around theedge 142 of the connection reference wall and positioned through theslits in pocket IDC+. Thus, the phase-A interconnect wire 94Ainterconnects all of the pockets IDC+ of the segments S-1, S-4, S-7 ofphase A. The interconnect wire 94A is eventually terminated at theoutboard slits of the pockets IDC+ on S-1 and S-7.

d. Common Interconnect

As shown in FIG. 12D, a neutral or common interconnect wire 96 isconnected in a forward direction. In this stitching step, portion of thecommon interconnect wire 96 is positioned in the common pocket IDC− onthe end cap for segment labeled S-1. As noted above, a trailing end ofthe wire for the winding coil of segment S-1 is also positioned throughpocket IDC− so that the interconnect wire 96 and the wire of the windingcoil can be electrically connected by an IDC (not shown) that will bepositioned in the pocket IDC− during later stages of assembly. From thepocket IDC−, the wire 96 is then routed in the clockwise directionaround the edge 142 of the connection reference wall on segment S-2,positioned in pocket IDC− on S-2, to high outboard ledge 122 on S-3. Thesame routing steps for the common interconnect wire 96 are then repeatedon each of the segments S-3 through S-9. Thus, the common interconnectwire 96 interconnects all of the neutral pockets IDC− of the segmentsS-1 through S-9. The interconnect wire 96 is eventually terminated atthe outboard slits of neutral pockets IDC− on segments S-1 and S-9.

In FIGS. 12A-12D, the preferred stitching patterns for the phase andcommon interconnect wires to connect the winding coils into the desiredphase arrangement are only exemplary. Other stitching patterns can beused without departing from the teachings of the present disclosure. Inone example, one or more of the above stitching patterns for the phasesmay be performed in an opposite direction around the stator 10. Forexample, another stitching pattern can involve first connecting phase Cwinding coils of FIG. 12A in a forward direction (e.g., clockwise),second connecting phase B winding coils of FIG. 12B in a backwarddirection (e.g., counterclockwise), third connecting phase A windingcoils of FIG. 12C in a forward direction, and lastly connecting theneutral ends of all the winding coils of FIG. 12D in a backwarddirection. Furthermore, with the benefit of the present disclosure andthe exemplary stitching pattern disclosed above, a person skilled in theart can develop such a pattern for a stator having more or less segmentsand/or more or less phases than those of the exemplary embodiment.

e. Positioning of IDCs and Other Assembly Steps

After stitching the interconnect wires as described above, IDCs arepositioned in the IDC pockets IDC+, IDC− and forced onto the wirespositioned through the pockets IDC+, IDC−. As is known in the art, IDCselectrically connect the plurality of wires positioned in the IDC pocketand provide a terminal coupling for connecting to a terminal end of thewire leads for the phases. Preferably, insulation displacementconnectors (IDCs) manufactured by Tyco are used with the disclosedstator assembly 10 and end caps 50. Excess portions of the interconnectwire as well as the posts 148 on the outboard side of the stator 10 aretrimmed, and the stator 10 may be positioned in a shell.

Final assembly steps involve connecting power leads to the statorassembly. For a three phase machine, for example, ¼-inch IDCs can beinserted into three of the IDC pockets IDC+ on the lead end caps 50,such as those on the end caps of segments S-1, S-2, and S-3. Terminalconnectors on the ends of three power leads can then be connected tothese ¼-inch IDCs. Finally, the power leads can be attached to thestator assembly using poke-in tie wraps having ends that insert into theholes (66 in FIG. 12D) in the lead end caps 50.

H. Scalloped Stator

In addition to the features disclosed above, the disclosed segmentedstator 10 includes additional features related to the contour of thestator 10, oil cooling and draining, material efficiency, and uniformfit of the stator 10 in a shell. As discussed in the Background Sectionof the present disclosure, hermetic motors used in compressors have anoil pump on the bottom of the compressor, known as the oil sump.Typically, the oil is pumped up through a hollow in the rotor shaft,past the motor, and to the main bearing. After lubricating the mainbearing, the oil is let loose on the lead-end or “topside” of the motorto drain back to the oil sump.

Returning oil is substantially prevented from returning through the bore11 of the stator 10 due to the winding coils 92 and the rotating rotor.Therefore, the outboard contour of the stator 10 can play a significantrole in how the oil is allowed to return to the oil sump from thelead-end of the motor. If there is not enough drain area in the motor,for example, the oil can become dammed on the topside of the motor,causing higher oil circulation in the refrigeration system, starvationof oil to the pump, and poor performance of the compressor due to thecompression of oil rather than gas in the system. On the other hand, ifthere is too much drain area in the stator, then the stator may beformed with less stator back iron than desired, which can create highermagnetic flux saturation in the stator core and can reduce theperformance of the motor.

Referring to FIG. 13, flux density paths are schematically illustratedon an exemplary embodiment of the disclosed segmented stator 10according to certain teachings of the present disclosure. In the presentexample, the disclosed stator 10 includes nine segments 20. The segments20 are electrically connected together into the annular shape of thestator 10 and contained in a shell S, which is shown in outline in theFIG. 13. The segments 20 have winding coils (not shown) that are woundabout their tooth portions 24 and that are separated by insulationmaterial, such as plastic strips. The pole ends 26 of the segments 20define a bore 11, and a rotor 14 is positioned within the bore 11 forrotation relative to the stator 10. In the present embodiment, the rotor14 includes a plurality of interior permanent magnets 16 and can besimilar to the rotors disclosed in U.S. patent application Ser. No.10/229,506, entitled “Permanent Magnet Machine” and filed Aug. 28, 2002,which is incorporated herein by reference in its entirety.

Each segment 20 of the stator assembly 10 in the present embodimentincludes features for oil draining. In contrast to the use of flatportions or cutaways on the outside of a stator as is typically done inthe prior art, each segment 20 defines a scalloped contour 36 formed inthe outside edge 30 of the segment. Consequently, the disclosed stator10 formed from the plurality of segments 20 has a plurality of suchscalloped contours 36 arranged symmetrically around the outside of thestator 10. The scalloped contours 36 in the segments 20 of the stator 10provide a symmetrical drain area around the circumference of the stator10 and shell S for oil to drain past the motor. The symmetrical drainarea may also provide the additional benefit of uniform motor cooling.

Referring to FIG. 14, an embodiment of a segment 20 for the disclosedstator assembly is shown in plan view relative to the circumference ofthe shell S. The circumference of the shell S is defined by a largeradius R₁, and the pole end 26 of the segment 20 is defined by asmaller, concentric radius R₂. The tooth portion 24 of the segment 20has a width W. Preferably, the scalloped contour 36 is defined in theoutboard edge 30 of the segment 20 by a third radius R₃. The segment 20is preferably symmetrical about a central line C, except for the ridgedand slotted ends 32 and 34.

1. Contact Area

The amount of contact area between the stator 10 and the circumferenceof the shell S is one concern in designing the scalloped contour 36 ofthe disclosed segment 20. In FIG. 13, for example, at least a minimumcontact area is required between the outboard edges 30 of the pluralityof segments 20 and the shell S that holds the stator 10 in place.Typically, the contact area of about 18-25% of the total circumferenceof the shell S is desired to hold the stator 10 in place. As shown inFIG. 14, the outboard edge 30 of the disclosed segment 20 contacts thecircumference of the shell S with a contact area A₁+A₂. Therefore, thescalloped contour 36 is preferably formed in the segment 20 so that thecontact area A₁+A₂ between the outboard edge 30 and the circumference ofthe shell S is about 18-25% of the entire angular expanse of the segment20. In this way, the stator 10 of FIG. 13 formed from the plurality ofsegments 20 can have the desired contact area between the outboard edges30 and the shell S, and the radius R₃ of the scalloped contours 36 asshown in FIG. 14 can also be selected to maximize the drain area A₃provided by the contour 36.

2. Shell Deformation

Returning to FIG. 13, potential deformation of the shell S by the stator10 is another concern in designing the scalloped contours 36 on thesegments 20. Being symmetrical about the circumference of the stator 10,the scalloped contours 36 of the segments 20 can give a superior fitbetween the stator 10 and shell S. Furthermore, the scalloped contours36 being symmetrical about the circumference of the stator 10 canequally deform the shell S if potential deformation occurs. As noted inthe Background Section of the present disclosure, the prior art thatuses flat portions around the outboard edge of a stator. Unlike theprior art, the symmetrically arranged scalloped contours 36 on thestator 10 reduce the flat length of the stator 10 that can interfereswith the shell S, which can reduces undesirable deformation of the shellS. As best shown in FIG. 14, the scalloped contour 36 in the segment 20preferably has sweeping radii R₄ on both ends of the contour 36 where itmeets with the outside edge 30 that contacts the shell S. The sweepingradii R₄ substantially removes sharp edges on the outboard edge 30 ofthe segment 20 and can potentially reduce deformation of the shell S.

3. Flux Density

In the example alignment between the rotor 14 and stator 10 shown inFIG. 13, the segments S-2, S-5, and S-8 have concentrated flux paths.Maintaining a sufficient amount of back iron on the stator 10 to avoidflux saturation in the segments 20 is yet another concern when designingthe scalloped contours 36 of the stator 10. As noted above, prior artsolutions can reduce the amount of back iron on a stator needed fordesired performance of a motor. Not only does the present embodiment ofthe scalloped contours 36 give more oil drain area and substantiallyreduce shell deformation, but the disclosed scalloped contours 36substantially maintain the back iron in the segments 20 at a preferredlevel.

In FIG. 14, the segment 20 is shown with the central line C thatsymmetrically divides the segment 20. A first line P₁ is shown from aninner corner 31 of the tooth portion 24 to the central line C of thesegment 20 and is substantially perpendicular to the central line C. Asecond line P₂ is shown from the inner corner 31 to the edge 30 of thesegment 20 and is substantially parallel to the central line C. Fluxpaths are schematically shown in FIG. 14 passing through the first andsecond lines P₁ and P₂ as the flux paths pass around the corner 31between the tooth portion 24 and the end 32 of the segment 20. The firstline P₁ defines a cross-sectional area represented by half of the widthW of the tooth portion 20.

To avoid issues with saturation, the second line P₂ preferably defines across-sectional area at least equal to that defined by the first lineP₁. The flux paths are also shown in FIG. 14 passing through arbitrarylines U and U′ that extend from the corner 31 of the segment 20 to thecentral line C and the scalloped contour 36. To avoid issues withsaturation, these arbitrary lines U and U′ preferably definecross-sectional areas at least equal to that defined by the first lineP₁. In this way, the scalloped contour 36 is formed in the segment 20 sothat the portion of the segment 20 between the corner 31 and thescalloped contour 36 has a sufficient amount of back iron for the fluxpassing between the tooth portion 24 and the ends 32 and 34 of thesegment 20.

I. Drain Holes in Lead End Caps

Returning again to FIGS. 6A through 6F, the lead end cap 50 in thepresent embodiment also includes features for oil cooling and draining.As best shown in FIG. 6B, the body portion 60 on the lead end cap 50defines the cavity 61 for molding purposes because the end cap 50 isinjection molded from plastic. The body portion 60 also defines themounting hole 66 for a cable tie (not shown). Not all of the mountingholes 66 on the lead end caps 50 on the completed stator assembly willhave a cable tie attached. For example, on the exemplary three-phasemotor, only three cable ties will be coupled in mounting holes 66. Thus,a number of open mounting holes 66 will expose the cavities 61 of theend caps 50. Because the motor in a hermetic compressor application isin an oil environment, oil can pass into the cavity 61 of the end cap 50through the mounting hole 66 when the cable tie is absent. Also, oil canpass through other holes in the end cap 50, such as the alignment holes146 or window 125 best shown in FIGS. 6A and 6B. Consequently, oil cancollect in the cavity 61 of the end cap 50 and can accumulate on thelead-end of the stator, which is undesirable.

To prevent the collection of oil, the disclosed end cap 50 includesdrain holes 67 along the bottom edge of the end cap 50. Oil drawn intothe cavity 61 from the exposed mounting hole 66 or other holes in thetop of the end cap 50 can drain out the bottom of the end cap 50 throughthe drain holes 67. The drain holes 67 substantially eliminate anypooling of oil on the lead-end of the stator segments 20 and on the topof the end cap 50. The drain holes 67 can reduce the amount of oilcaused to circulate through the compressor system by letting some of theoil to flow through the end cap 50 rather than traveling down throughthe bore of the stator 10. When oil travels through the bore of thestator, the spinning motion of the rotor can force the oil back up tothe top end of the compressor where the oil is then picked up by theflow of gas and circulated through the refrigeration system. Althoughthe drain holes 67 offer a small path for returning oil to the oil sumpof a compressor, it has been found that the drain holes 67 on end caps50 of a stator assembly 10 may prevent about 1-2 ounces of oil frompooling in the end caps 50 if the drain holes 67 were not provided. Inaddition, it is believed that the drain holes 67 can aid in cooling ofthe winding coil on the segments by facilitating the drain of oil.Moreover, the drain holes 67 at the bottom edge of the end cap 50 alsobeneficially act as relief areas for the interlock tabs (element 37 inFIG. 3A) on the segment.

As used herein and the appended claims, reference to words, such as top,bottom, above, below, inboard, outboard, lead-end, base-end, etc. havebeen used merely for clarity to show the relative locations ofcomponents on the disclosed end caps and stator assembly. Such words ofrelative location do not limit the orientation of the components and donot limit the overall orientation or operation of the disclosed end capsand stator in a motor.

The foregoing description of preferred and other embodiments is notintended to limit or restrict the scope or applicability of theinventive concepts conceived of by the Applicants. In exchange fordisclosing the inventive concepts contained herein, the Applicantsdesire all patent rights afforded by the appended claims. Therefore, itis intended that the appended claims include all modifications andalterations to the full extent that they come within the scope of thefollowing claims or the equivalents thereof.

1. An end cap for a segment of an electromagnetic machine having wire, the segment having a yoke portion with an outboard end, a tooth portion extending from the yoke portion, and a pole end on the tooth portion, the end cap comprising: a first inboard leg extending from the end cap and positioned adjacent one side of the tooth portion; a second inboard leg extending from the end cap and positioned adjacent another side of the tooth portion; an outboard leg extending from the end cap and positioned adjacent the outboard end of the yoke portion; and a surface positioned adjacent the segment, the surface defining at least one recessed area adjacent one of the legs for receiving a portion of material potentially scrapped from the one leg when the end cap is positioned on the segment.
 2. The end cap of claim 1, wherein the first and second inboard legs each have a face positioned against an outboard face of the pole end.
 3. The end cap of claim 1, wherein the outboard leg positions within a slot defined in the outboard end of the yoke portion.
 4. The end cap of claim 1, wherein the first and second inboard legs each have an edge positioned against the side of the tooth portion with the interference fit.
 5. The end cap of claim 1, wherein the first and second inboard legs each have a distal end, each of the distal ends substantially meeting with the distal end of the inboard leg on another end cap positioned on an opposing surface of the segment.
 6. The end cap of claim 5, wherein the first and second inboard legs on the opposing end caps substantially cover an outboard surface of the pole end of the segment.
 7. The end cap of claim 1, wherein the end cap includes: a body portion positioned adjacent the yoke portion and having an inboard side substantially perpendicular to the tooth portion, an inboard wall positioned adjacent the pole end and having an outboard side, the outboard side substantially opposing the inboard side of the body portion; a winding portion positioned adjacent the tooth portion and connected between the body portion and the inboard wall, the winding portion having an angled surface, the angled surface angling from the winding portion to the outboard side of the inboard wall and configured to position wire in the area between the body portion and the inboard wall.
 8. The end cap of claim 7, wherein the first and second inboard legs each have an angled surface on an outboard side of the leg, the angled surface angling from the side of the tooth portion and configured to position wire in the area between the pole end and the yoke portion.
 9. The end cap of claim 8, wherein the angled surface of the inboard wall and the angled surfaces of the inboard legs define substantially the same angle relative to the tooth portion.
 10. The end cap of claim 9, wherein the angled surface of the inboard wall transitions smoothly to the angled surfaces of the inboard legs.
 11. The end cap of claim 7, wherein the first inboard leg is positioned with an interference fit; and the second inboard leg is positioned with an interference fit.
 12. The end cap of claim 11, wherein the first and second inboard legs each have an angled surface on an outboard side of the legs, the angled surface angling from a side of the tooth portion and configured to position wire in the area between the pole end and the yoke portion.
 13. The end cap of claim 12, wherein the angled surface of the inboard wall and the angled surfaces of the inboard legs define substantially the same angle relative to the tooth portion.
 14. The end cap of claim 13, wherein the angled surface of the inboard wall transitions smoothly to the angled surfaces of the inboard legs.
 15. The end cap of claim 11, wherein the first and second inboard legs each have a distal end, each of the distal ends substantially meeting with the distal end of the inboard leg on another end cap positioned on an opposing surface of the segment.
 16. An end cap for a segment of an electromagnetic machine having wire, the segment having a yoke portion with an outboard end, a tooth portion extending from the yoke portion, and a pole end on the tooth portion, the end cap comprising: a plurality of legs extending from the end cap; and a surface adapted to be positioned adjacent the segment, the surface defining at least one recessed area adjacent one of the legs for receiving a portion of material potentially scrapped from the one leg when the end cap is positioned on the segment.
 17. The end cap of claim 16 wherein the plurality of legs form an interference fit with the segment when the end cap is positioned on the segment.
 18. The end cap of claim 16 wherein the plurality of legs includes a first and a second inboard leg, the first and second inboard legs each include an angled surface on an outboard side of the legs, each angled surface extending from a side of the tooth portion and configured to position wire in the area between the pole end and the yoke portion when the end cap is positioned on the segment.
 19. The end cap of claim 18 wherein the first and second inboard legs each have a distal end, each of the distal ends adapted to extend and contact the distal end of the inboard leg of a like end cap positioned on an opposing surface of the segment when said end caps are positioned on the segment. 